In recent years, internet and digital electric home appliances have rapidly become popular and it has been required for information processing in communication systems and computers to have high capacity and high speed, and therefore it has been investigated that high capacity data is transmitted at a high speed by a high frequency signal. However, when transmitting high-capacity data by a high frequency signal, a conventional transmission system by electric wiring has a high transmission loss, and therefore a transmission system by light has been actively investigated and intended to be used for wirings for communication between computers, and for communication in an apparatus or a board, and the like. An optical waveguide which is one of elements for realizing such transmission systems by light is a basic constitutional element in optical elements, optical interconnections, optical wiring boards, opto-electric hybrid circuit boards, and the like, and therefore the optical waveguide has been required to provide high performance and to be low cost.
A quartz waveguide and a polymer waveguide have been heretofore known as the optical waveguide. Among these, the quartz waveguide has a characteristic of extremely low transmission loss in a range of wavelength of 600 to 1600 nm used in a transmission system by light, but has a demerit from the viewpoint of a production process and cost such as high processing temperature and difficulty in production of a waveguide with a large area.
On the other hand, since the polymer waveguide is formed using a photosensitive resin composition, it has such advantages as providing easy processing and having a high degree of freedom for material design, and therefore those using polymer materials such as PMMA [poly(methyl methacrylate)], epoxy resins, polysiloxane derivatives have been investigated. For example, Patent Documents 1 and 2 each describe a polymer waveguide using an epoxy compound. Further, Patent Document 3 describes a waveguide using a polysiloxane derivative.
However, there has been suggested such a problem that the polymer waveguide generally has low heat resistance and high transmission loss in a range of wavelength of 600 to 1600 nm used in a transmission system by light. In order to solve this problem, there have been investigated, for example, a method for reducing transmission loss by chemical modification such as deuteration and fluorination of the polymer, and a method of using polyimide derivatives such as fluorinated polyimide with heat resistance. However, these methods have disadvantages, for example, that the deuterated PMMA has low heat resistance, and that although fluorinated polyimide is excellent in heat resistance, a dry etching process is necessary for forming a waveguide pattern as well as in the case of the quartz waveguide, and thereby production cost is increased.
Patent Document 1: Japanese Patent Application Laid-Open No. 10-170738
Patent Document 2: Japanese Patent Application Laid-Open No. 11-337752
Patent Document 3: Japanese Patent Application Laid-Open No. 9-124793